Well, I guess it was just a matter of time.
Background: I have two tanks, a 20 long (pH 7.2) and a 10 (pH 7.0). Both are fully cylced: the 20 using 12 zebra danios, and the 10 using 7 danios. Current readings are Ammonia = 0, NitrIte = 0, NitrAtes = 5ppm.
Last week, the 10 gallon began...